Heat exchangers are generally formed of a core configured to facilitate an exchange of thermal energy with a fluid passing therethrough. A header is disposed on at least one end of the core, and provides an interface between the core and a fluid reservoir, such as a tank or manifold. One common type of header is known as a recessed header, wherein a portion of the header is recessed to receive a portion of the fluid reservoir therein.
In modern heat exchangers, an integrated means for coupling the fluid reservoir to the header is desirable, as it allows the heat exchanger to be assembled without using independent fastening means, such as bolts and clips. By using an integrated means for coupling the headers and fluid reservoirs, manufacturing costs can be substantially reduced by minimizing assembly time and eliminating unnecessary components.
However, in recent years, increased performance requirements for heat exchangers have caused existing configurations of integrated coupling means to become insufficient. For example, modern heat exchangers operate at increased internal pressures. During operation at the increased internal pressures, the interface between the header and the fluid reservoir may warp or fracture as a result of pressure induced stresses, causing a failure of the heat exchanger.
In a common heat exchanger configuration, a fluid reservoir is coupled to a header by inserting a portion of the fluid reservoir into the header, and subsequently securing the fluid reservoir by a crimping process or deforming a plurality of tabs of the header over the inserted portion of the fluid reservoir. However, this configuration is prone to failure under the increased pressure conditions of modern heat exchangers. For example, as the pressure within the fluid reservoir increases, the fluid reservoir is biased apart from the header, and the inserted portion of the fluid reservoir applies a bending moment to the tabs of the header. The bending moment forces the tabs of the header outward, allowing the fluid reservoir to separate from the header. Further, deforming the tabs of the header creates residual stress concentrations in the header. Upon application of the increased pressures, the areas of the residual stress concentrations are prone to failure.
Additionally, modern heat exchangers are commonly integrated into rigid components of the vehicle. By rigidly mounting the heat exchanger within the vehicle, the heat exchanger is more susceptible to harmful vehicle vibrations. Accordingly, increased vibration of the heat exchanger further increases stresses in the interface between the header and the fluid reservoir.
In order to solve the problem of increased vibration, a strength, stiffness, and durability of the header is increased. By increasing the strength, stiffness, and durability of the header, an increased bending force is required to crimp or otherwise deform the plurality of tabs of the header over the fluid reservoir. The increased force causes the header to be more susceptible to distortion and deformations due to the residual stress concentrations therefrom. Additionally, some heat exchangers include heat exchanger tubes received by the header. The tubes minimize distortion of the header. However, other types of heat exchangers have headers that do not receive tubes, such as water-cooled charge air coolers, for example. The increased force applied to headers that do not receive the tubes escalates susceptibility of distortion to such headers.
Accordingly, there exists a need in the art for an improved means of coupling a fluid reservoir to a header of a heat exchanger, wherein the coupling means is integral to the heat exchanger assembly.